Labeled Insulin Catabolism in Chronic Renal Failure and in the Anephric State

Abstract

The influence of the kidney in the catabolism of insulin was investigated by comparing the metabolic clearance rate of labeled insulin in control subjects, in patients with chronic renal failure and in anephric patients, both groups being treated for several months by iteral dialysis. The methodology involved the constant infusion (23 ng./kg./min.) of mildly iodinated (mean iodination degree inferior to 0.2 atom/molecule) I-125-insulin, the estimation of the plasma content in labeled insulin by chromatoelectrophoresis, and the use of an analog and a digital computer for the calculation of the metabolic clearance rate. In patients with chronic renal insufficiency and in anephric patients a marked reduction of the metabolic clearance rate (MCR) was observed and the extent of this reduction was comparable in these two groups of patients. The findings confirm the part played by the kidneys in the metabolism of insulin anddemonstrate that in serious chronic nephropathies, the kidneys have completely lost their ability to catabolize insulin. They also provide an explanation for the reduced insulin requirements observed in certain cases of diabetes complicated with a nephropathy.